Add libgmp 6.2.0 to third_party
Don't build it yet. That will come in the next review.
Change-Id: Idf3266558165e5ab45f4a41c98cc8c838c8244d5
diff --git a/third_party/gmp/mpz/tstbit.c b/third_party/gmp/mpz/tstbit.c
new file mode 100644
index 0000000..48725d4
--- /dev/null
+++ b/third_party/gmp/mpz/tstbit.c
@@ -0,0 +1,80 @@
+/* mpz_tstbit -- test a specified bit.
+
+Copyright 2000, 2002 Free Software Foundation, Inc.
+
+This file is part of the GNU MP Library.
+
+The GNU MP Library is free software; you can redistribute it and/or modify
+it under the terms of either:
+
+ * the GNU Lesser General Public License as published by the Free
+ Software Foundation; either version 3 of the License, or (at your
+ option) any later version.
+
+or
+
+ * the GNU General Public License as published by the Free Software
+ Foundation; either version 2 of the License, or (at your option) any
+ later version.
+
+or both in parallel, as here.
+
+The GNU MP Library is distributed in the hope that it will be useful, but
+WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+for more details.
+
+You should have received copies of the GNU General Public License and the
+GNU Lesser General Public License along with the GNU MP Library. If not,
+see https://www.gnu.org/licenses/. */
+
+#include "gmp-impl.h"
+
+
+/* For negatives the effective twos complement is achieved by negating the
+ limb tested, either with a ones or twos complement. Twos complement
+ ("-") is used if there's only zero limbs below the one being tested.
+ Ones complement ("~") is used if there's a non-zero below. Note that "-"
+ is correct even if the limb examined is 0 (and the true beginning of twos
+ complement is further up).
+
+ Testing the limbs below p is unavoidable on negatives, but will usually
+ need to examine only *(p-1). The search is done from *(p-1) down to
+ *u_ptr, since that might give better cache locality, and because a
+ non-zero limb is perhaps a touch more likely in the middle of a number
+ than at the low end.
+
+ Bits past the end of available data simply follow sign of u. Notice that
+ the limb_index >= abs_size test covers u=0 too. */
+
+int
+mpz_tstbit (mpz_srcptr u, mp_bitcnt_t bit_index) __GMP_NOTHROW
+{
+ mp_srcptr u_ptr = PTR(u);
+ mp_size_t size = SIZ(u);
+ unsigned abs_size = ABS(size);
+ mp_size_t limb_index = bit_index / GMP_NUMB_BITS;
+ mp_srcptr p = u_ptr + limb_index;
+ mp_limb_t limb;
+
+ if (limb_index >= abs_size)
+ return (size < 0);
+
+ limb = *p;
+ if (size < 0)
+ {
+ limb = -limb; /* twos complement */
+
+ while (p != u_ptr)
+ {
+ p--;
+ if (*p != 0)
+ {
+ limb--; /* make it a ones complement instead */
+ break;
+ }
+ }
+ }
+
+ return (limb >> (bit_index % GMP_NUMB_BITS)) & 1;
+}